Finishing of aviation naphthas



Patented Feb. 17, 1948 Delaware kpi uation January-29, 194s;s'er'i'a1 Noi'e44j15'2 4'Claims. (01. 196-40) quanfiity-br high-made aviation ruel. The cad-,alyjsic eracking of hydrdb'a rbon disoctan "1mmb eris e wefl kr'iown proce ure in fSince low boiling ha e mium 1 V the same time have "e ati l i1 jli enfise edrll s j pres- Other as AFD'3-G. These-ratings ha definite meanings to those epgaged 1n the production of aviation fuelland foritpie purpoisiej qfithi s description need'jot "be eiaborated on further.

Hydrogenation, c ertjs olefins to 'parafims. r'is 'e'speqie-ny ispparaflins, ehelrecterieties and at Y ;.is@ $fecw F 3-0 characteriefis, "hydrogenation tends to imn he that high as iqhat "it converts 16w jbbilihgpieilins mm igdplraf- 'AFD 14C aiidfAFD 3-0 characteristics so that reis un esi able {to onve 'rt high boiling olefir'is Acid tr atmefipff llbwee by 'redistillettiioh, re-

qfn'oves ol efiiis whiehfare'of poor 1-0 rating eind al'so of poor rating When used to operate a motoron a rich mikt'ure Hence, acid treatment hasjhe effiect of 'iiacreas'in'g' both the AFD l-C and ithe-AFD- 3=C ratings. This pro- "oedure, ho wejl er the d'isadvanpege's of not -b'e'irig abcompaInid-byiireatmg losses.

Thermal recracking operations, on the other ha'hd, tend 15o convert "both high honing Olefins 'a'ifid high boiling pd flins partly to lower and higher boiling olefi s and arny to aromatics. This operation 'iihefefiegit of increasing both 1-'C nd 310 ratings as a result of removing the high boning p'araflins having lower -produced 'in "fil'i eopfti dn iloss of material, as compared "with hydrogenation, "also respl ts from jthis Operation. By combining 'recrackm'g,

acid treating "and remefllldtidn operations, furt-hr increases in-beth i-C *dnd 3-0 ratings over those obtainable by recracking or acid treating operations, taken alone, may be achieved.

According to the present invention, the efl'iuent from a catalytic cracking operation is processed in such a way as to impart to it the maximum AFD 1-C and AFD 3-0 ratings for a given yield. This is accomplished according to the present invention by dividing the efiluent into fractions. There should be at least two fractions, one boiling between about 110 F. and 210 F. and the other boiling between about 210 F. and 330 F. If desired, a third fraction boiling between about 210 F. and 270 F. is segregated in which case the second fraction will boil between about 270 F. and 330 F.

In operating according to the present invention, the lowest boiling fraction is always hydrogenated. The highest boiling fraction is always subjected to a processing which includes a recracking treatment and a treatment with concentrated sulfuric acid of the conventional type, T

referred to above, followed by redistillation.

The intermediate fraction may be treated similarly to either of the other two fractions. In

certain cases, it may be found preferable to hydrogenate the intermediate fraction in which 4 usually employed in pellet form. The hydrogenation unit, illustrated by a single rectangle in the drawing, includes the usual auxiliary equipment, such as condensers and fractionators, from which is recovered a hydrogenated product which is conducted by line I3 to an accumulator 14, out of which it is fed out of line [5 into a blending line [6.

The middle stream, as shown in the drawing, is conducted by line [0 provided with a valve H to an acid treating unit 18 from which the acid treated product is discharged through line into a still 20 from which the refined product is recovered overhead through line 2| and conducted to an accumulator 22 which is also connected to blending line 16 by line 23. The polymers formed during the acid treatment are removed as bottoms from still 2 0 through line 24.

The bottom fraction is fed byline 'l I re a thermal cracking unit 25. This unit is operated at a temperature within the range of about 900 to 1100 Rand under a pressure of between about 700 to 900 pounds per square inch. Again, with respectto this unit, it is to be understood that the rectangle 25 includes all of the auxiliary equipment, such as separators and fractionators,

. required to isolate the desired product of a boilcase it is combined with the lowest boiling fraction during the hydrogenation of the latter.

Alternatively, it may be desirable merely to acid treat and redistillthe intermediate fraction, although the heaviest fraction is recracked, acidtreated and redistilled. Finally, the intermediate fraction may be combined-with the heaviest fraction and subjected to the same treatment as the latter.

The nature of the present invention may be better understood from the following detailed description of the accompanying drawing in which thesingle figure-is a front elevation in diagrammatic form of anapparatus in which the various types of treatment employed in the present invention'may be conducted.

Referring to the-drawing in detail, numeral I designates a-catalytic cracking unit. A conventional gas oil is fed through line 2. The efliuent from the catalytic cracking unit is discharged into a fractionator 3 from which fixed gases are withdrawn at the top through line 4. Bottoms are withdrawn from the fractionator 3 through.

line 5. One or more recycle cuts are withdrawn as side streams through outlet 6 and naphtha is withdrawn as a side stream through line 1. This -naphtha eut will usually have a boiling range from about 110 F. to about 330 F. It is fed to, a second-fractionator 8 which is so operated as to provide three side streams, the upper boiling between about 110 F. and 210 F. being carried ofi through line 9, the middle boiling between about 210 F. and 2'70 F. being carried off through line in and the. bottom boiling between about 270 F. and 330 F. being carried oir through -line H.

Line 9 feeds the light fraction to a catalytic hydrogenationunit 1 2. The details of this bydrogenation step are well known in the art and do not constitute a part of the present invention. In general, thi hydrogenation is of the non-destructive type carried out at a temperature ranging between 400 F. to 700 F. and under a pressure of between 100 to 1'50 pounds per square inch while utilizing an active hydrogenation catalyst as an example of which may be mentioned a catalystcomposed of about '2 parts of nickel sulfide and '1' part of tungsten sulfide.

ing range substantially the same as the feed to theunit 25, which is conducted from the unit through line 26 to an acid treating unit 21 from which the refined hydrocarbons are fed through line 28 to line 19 and into sun 20. v

It is to be understood with respect to both of the acid treating units, represented in the drawing by rectangles i8 and 21, that these units include all auxiliary treatments associated with conventional acid treatment such as sludge separation, and water washing and alkali neutralization of the oil.

Line In is connected to line 9 by line 29 provided with a valve 30. It is also connectedto so-supply of high octane blending agents 33. These blending agents will ordinarily be isoparaffinsof suitable boiling range either obtained by distillation or by alkylation of olefins, alkylated aromatics, hydrogenated polymers, selected aromatics and the like.

Reference is made to the. following table in which are compiled data showing the effect of difi'erent processing steps on the AFD l- C and AFD 3-C ratings ofthe three fractions of catalytic cracking eiiluent discussed above. In. this table the fractions identified; are fractions of 'a cracked eflluent obtained by'catalytically'craclring mixed parafiinc gas oils with approximately conversion per pass at a reactor tempera;- -ture of 945 F., a catalyst oil-- ratio of 4.3 and weight of oil per hour per weight of catalyst of $9 (W./hr./W;).. The hydrogenation was conducted at a temperature of about 500 F. with a pressure of about pounds-per square inch and in the presence of a catalyst composed of nickel sulfide and tungsten sulfide. The acid employed for the acid treatment was 9.8% sulfuric acid. .The thermal after-treatment -(recracking) was conducted at a temperature of about 930 F. under=a pressure of about '750 pounds per square inch witha-feed rate of 5100 barrels per streamrd'ay.

assorted:

The octane and'irlchsmixtureadataiairen are based on. correctionaof;earthitaction T1027 pounds Reid vapor pressureiwithi iscxpentane and additiomof hcstetraethylilead per-gallon.v

thatdfidesiredfithis;rractiomcangbezincliidcdi with the first fraction in the hydrogenation; j

Elie; heaviesti fraction. shows; very; little: im-

provementiini thesAZFDZI-I-Cand 3+Gznatings- Tarts" Comparison. of, atclyticalzg c eck-8d naphthasi 1 finished, by, (19s hydrogenation, (2 atreatment. with-,1 Moundaamcid per." ba rel cnd (-3.).- the?! maZ-rec-rackingml s. 1 fli-eoundsbi-caid per barrel.

110?210 F. Fraction:

A'FD-1G Octane No;+4'cc; TEL/Gal;

AJSD 3+.C RichMixture, as Index No Bromine No SillfmwWt; Percent..-

AFD 1'G Octane Noel-4 cc. TEL/Gal;

A-FD BTGjRKOhZIVIiXt IXGLRS index No.

270=330 F5 Fraction:

AFD-150..Octane ;No.+4'cc;HEEL/Gal AED 3 Q-RichMixture. as Index No Bromine 'No: Aromatic Content. Vol. Per cent. Sulfur. Wt. Per cent Yield'based on'raw*l'l0330 F. fraction, Vol. Per cent MethodofFlnlshing A p d f e a t Iher mal Re in... 7-1. .w, 3 2252 5; Hydrogena. inggmd figgggfgg} .era'ckmgiio tion tiOll" I Thermal r lbs:

Rem ki is l/bbl 7 Units.

sac- 94:1 84.0- 89:9 95.6 1.4%. 1116;, 23. is; 6 1.5.. 111.0 54.2 21.1 3 3051 aa-e- 36:9- one ,0: 1 0.0.2. 0.0a 22.0 22.0 I 22.0 20.9 13.3 sea- 95:9 1.40; 5.4-1 99.0 127 7 12s 127 136; 15 9 1910= 1 1.4; 19.9 14.7: 4.6 cm. 64.:9- V 67: 1-= 71. 5: 8e. 5 0.04.. 0. 02. p 0.05 acresa-a .9 30 2 24.7

Referrlngto thistable, itwill. be seen that ydrogenation of the light fraction resultsin an increase of over 9 in the AFD l-C rating with a 100% yield. When this light fraction is merely acid treated, the AFD 1-C rating is increasedpnlii: about 2.5 and the AFD 3-6 rating iS"-a;1SQY* increased about 8.5. It is to. be. noted, however, that; there is; a considerable lossof yield: in. the order of 20%. It may be observedv here that the fractionused for the acid treatment and. comb-ination thermal and acid treatment was from a different catalytic cracking effluent than that used for the hydrogenation. The data given, however, are for the purposes of comparison and are competent for indicating the order of improvement.

When the light fraction is given a thermal recracking treatment followed by acid treatment, the AFD l-C rating is increased about 4 points and the AFD 3-0 rating is increased about 15 points, but the yield is decreased more than Referring to the middle fraction, it will be observed that hydrogenation increases the AFD l-C rating about 6.5 points, but decreases the AFD 3C rating by 2 points with a 100% yield. Acid treatment of this middle fraction results in an increase in AFD l-C rating of 5.9 and an increase in AFD 3-C rating of 7 with a loss of yield amounting to about 9%. When this fraction is given a thermal recracking treatment followed by acid treatment the AFD l-C rating is increased 11.6 points and the AFD 3-C rating is increased 28 points with a loss of yield of about 37%. Here it will be seen that as to this fraction there is a much greater increase in AFD 1-0 and AFD 3-C ratings for a given loss of yield than in the case of the first fraction where thermal treatment followed by acid treatment is employed. It is to be noted, however, that with this fraction improvement of the same order of magnitude of the AFD 1-C rating is obtained by hydrogenation as with the first fraction indicatby. hydrogenation. there. being, an. inc iease of about .2 points inr theiormeranda decrease of, 1-v point in thelatter.

Acid ea ina; h w r oithise raction r ulted in, an increase of. 14.45 polntsin the-AFD 12C.v rating; and in. .9. poi-ntsin the-AFD 3-C rating withavery minoklnss in yield; This. fractionwas subjected: to thermal-treatment;followed by: aeidtreatment and; showed an:.increase. in: the AFD;- leC. rating 0i. 8; points: and; in: theAFQ 3.-G: ratin o 3: points with a loss of yield of about 20%. Since it is this combination treatment which also gave considerable improvement in the AFD 3-0 rating of the middle fraction, the latter will be processed so with the third fraction or with the first fraction depending upon Whether it is desirable to build up the AFD 1-C rating or the AFD 3-C rating.

From the data shown, it will be clear that the maximum improvement in AFD l-C rating and AFD 3-0 rating for a given yield can be realized by hydrogenating the fraction boiling between about F. and 210 F. and subjecting the fraction boiling between about 210 F. and 330 F. to recracking followed by acid treatment and redistillation. This is the preferred mode of operation according to the present invention.

It is to be understood that the references to cuts having certain boiling ranges herein are not intended to establish fixed limits on these boil ing ranges, but are intended only to indicate the character of the difierences in boiling ranges of the separate fractions which are subjected to difierent treatments. It is quite clear, from the fact that the middle fraction responds satisfactorily either to the treatment preferred for the first fraction or the treatment preferred for the third fraction, that the end boiling point of the first fraction can be any place between 210 F. and 270 F. or slightly higher. By the same token the initial boiling point of the third fraction can be anything between 270 F. and 210 F., or slightly lower. I

The nature and objects of the present invention having been fully described, what I wish to claim as new and useful and to secure by Letters Patent is:

fnamed fraction to a refining procedure includ- 1. A method for processing the eiiluent from a hydrocarbon catalytic cracking operation which comprises dividing said effluent into at least two fractions, one of said fractions comprising at least a major portion of constituents boiling between about 110 F. and 210 F. to the exclusion of constituents boiling above about 270 F. and

another of said fractions comprising at least a major portion of constituents boiling between about 270 F. and 330 F. to the exclusion of constituents boiling below about 210 F. and comprising parafilns and aromatics, subjecting the, first named fraction to catalytic hydrogenation subjecting the second named fraction to a refining procedure including thermal cracking to convert parafilns to olefins followed by treatment with concentrated sulfuric acid sufiicient to remove said olefins without substantially reducing the aromatic content thereof, and recombining said fractions after their respective treatments.

2. A method for processing the eilluent from a hydrocarbon catalytic cracking operation which comprises separating from said efiiuent two fractions, the first having a boiling range between about 110 F. and 270 F., and the second having a boiling range between about 270 F. and 330 F. and comprising paraifins and aromatics, subjecting the first fraction to catalytic hydrogenation, subjecting the second named fraction to a refining procedure including thermal cracking to convert paramns to olefins followed by treatment with concentrated sulfuric acid sufficient to remove said olefins without substantially reducing the aromatic content thereof, and recombining said fractions after their respective treatments.

3. A method for processing the eflluent from a hydrocarbon catalytic'cracking operation which comprises separating from said eiiluent two fracing thermal cracking to convert parafiins to olefins followed by treatment with concentrated sulfuric acid sufiicient to remove said olefins without substantially reducing the aromatic content thereof, and recombining said fractions after their respective treatments.

4. A method for processing the eiiluent from a hydrocarbon catalytic cracking operation which comprises separating three separate fractions 2 from said eflluent, the first having a boiling range between about F. and 210 F., the second having a boiling range between about 210 F. and 270 F., and the third having a boiling range between about 270 F. and 330 F. and comprising paraffins and aromatics, subjecting the first named fraction to catalytic hydrogenation, subjecting the second named fraction to treatment with concentrated sulfuric acid, subjecting the third named fraction to thermal cracking to convert 'parafiins to olefins followed by treatment with concentrated sulfuric acid sufficient to remove said olefins Without substantially reducing the aromatic content thereof, and recombining the several fractions after their respective treat- 'ments.

BOYD N. HILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,827,537 Morrell Oct. 13, 1931 2,276,081 McGrew Mar. 10, 1942 2,336,736 Kanhofer Dec. 14, 1943 2,383,056 Goldsby Aug. 21, 1945 2,401,363 Meier June 4, 1946 

